Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/16—Writing inks

Definitions

• the invention relates to a chemically correctable ink for write-erase systems, which is acidic and contains such dyes that can be decolorized with an alkaline ink erase liquid.
• ink eraser pens which are constructed in the manner of a fiber pen and contain a liquid which can decolorize ink.
• ink eraser pens are of particular interest to schoolchildren because they make it possible to chemically eliminate any writing errors that have occurred when writing with ink by simply brushing over with the erasing liquid. Compared to mechanical erasing, this gives the advantage of a simple and quick correction in which the structure of the paper surface in the correction area is hardly affected.
• the currently best and most common write-erase system in practice consists of inks based on triarylmethane dyes and extinguishing liquids based on sulfite-containing solutions. Lettering from these inks can be completely decolorized in a very short time by painting over with the extinguishing liquid without the paper quality being significantly and visibly changed. Extinguishing liquids that contain a basic nitrogen compound in the form of the free base as an effective extinguishing substance also work in the same way for inks based on triarylmethane dyes. Furthermore, as has been found, inks based on other dyes, namely on the basis of methine or polymethine dyes and xanthene dyes, can equally well be decolored with the same extinguishing liquids.
• the inks mentioned above are normally acidic because the dyes in question then have their optimal color strength.
• the most favorable pH value is in the range of about 1 - 3, depending on the specific dye.
• the extinguishing liquids have a strongly alkaline pH value in the range of, for example, 13 because the decolorization reaction between the ink dye and the extinguishing substance only occurs in alkaline environment expires.
• some ink dyes lose their color anyway in a strongly alkaline environment, even if no special extinguishing substance is present.
• the extinguishing liquid In order to make a faulty lettering with the extinguishing liquid disappear, the extinguishing liquid must be applied to the paper at least in such a sufficient dose that the required alkaline environment is established in the extinguishing area and that the extinguishing substance can become effective.
• the extinguishing liquid since in practice, especially by inexperienced and impatient pupils, the extinguishing liquid is mostly overdosed and, in addition, the extinguishing liquid normally also has a relatively high concentration of effective extinguishing substance, the inevitable consequence is that the extinguishing area will then no longer be new with the same ink can be overwritten.
• the invention is now to create an ink for write-erase systems with an alkaline extinguishing liquid which allows a correction area treated with the extinguishing liquid - after drying the same - to be overwritten again immediately with the same ink and consequently also with the same writing instrument .
• the ink contains an addition of 0.1 to 10% by weight and preferably 0.5 to 5% by weight of weak acids or acidic salts, which is added to the paper with the alkaline components of the Extinguishing liquid forms a weakly acidic buffer mixture.
• the acids or salts should have a pK s value> 0.
• a further aspect of the invention is the use of an addition of 0.1 to 10 wt.% Of a weak acid or an acidic salt with a pK a value> 0-containing ink on the basis of decolorizable dyes in an alkaline medium in Connection with an alkaline ink extinguishing solution.
• the ink can contain triarylmethane dyes, methine dyes or polymethine dyes and / or xanthene dyes.
• All weak acids or acidic salts that can be stably dissolved in the ink and are free from undesirable side effects (e.g. from a physiological point of view) can be used as an additive to the ink.
• Weak organic acids such as lactic acid, citric acid, tartaric acid and oxalic acid (including mixtures thereof) or acidic inorganic salts such as zinc chloride and aluminum sulfate are preferred.
• the amount of additive must be such that a buffer mixture with a sufficiently high buffer capacity results when a correction area is overwritten. Since the amount of alkali present in the paper is unknown and can also vary depending on the amount of extinguishing liquid applied, a certain "safety surplus" of additive is expediently used. This gives the limit values of 0.1 to 10% by weight and preferably 0.5 to 5% by weight.
• the additive especially if it consists of weak acids, can also be used to acidify the ink.
• a mineral acid such as sulfuric acid in the usual way to acidify the ink, because the pH of the ink is then brought to the optimum value for the color depth of the respective dye, regardless of the value that the weak acid would give can be.
• the weakly acidic buffer mixture that forms when a correction area is overwritten naturally does not buffer only the alkali in the paper, but also reduces the pH value of the ink in the correction lettering to the value specified by the buffer mixture.
• this fact does not bother us because the resulting color deviations are barely visible to the naked eye, in contrast to the often striking color deviations that have so far been the result of overwriting with a foreign ink.
• the erasure liquid that forms the write-erase system together with the ink is only required to require an alkaline environment for the erasure effect and to have no erasure effect outside the alkaline environment.
• the invention is therefore independent of the presence of certain special extinguishing substances.
• ink blue instead of ink blue, other triarylmethane dyes can also be used in all cases, e.g. Astrarhodulin blue, C.I. Basic Blue 1, or Duasynklareblau SN, C.I. Acid Blue 93.
• Astrarhodulin blue C.I. Basic Blue 1
• Duasynklareblau SN C.I. Acid Blue 93.
• composition of an ink with polymethine dyes are, for example, Astrazon Red 6B, CI Basic Violet 7, Astrazon Blue 5RL, CI Basic Blue 62, Astrazon Violet FRR, CI Basic Violet 20 or Astragelb R, CI Basic Yellow 44. These can be used analogously in the above formulation .
• composition of an ink with xanthene dyes is a composition of an ink with xanthene dyes:
• the inks according to the above exemplary embodiments were examined to determine whether they could be used to overwrite a correction range previously treated with various types of basic ink extinguishing liquids (solutions of a sulfite, a polyamine, a polyimine and of ethanolamine and ethanolamine sulfite, each adjusted to pH 13 with NaOH) .
• the correction area could be overwritten without any problems even if a relatively high dose of extinguishing liquid had previously been applied to the paper.
• the only prerequisite was that the correction area was completely dry, otherwise the correction lettering in the still wet paper tended to run.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

Applications Claiming Priority (4)

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Cited By (10)

Citations (3)

• 1980
  • 1980-12-15 EP EP80730078A patent/EP0032653A3/fr not_active Withdrawn

Patent Citations (3)

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